1. Technical Field
The present invention relates in general to carbon coated magnetic head sliders, and in particular to a smoothed slider surface or other surface and a method of smoothing the surface of a slider head or other substrate surface. Still more particularly, the present invention relates to an improved corrosion and impact resistant magnetic head slider that is ion milled prior to carbon coating to improve the coverage of the carbon layer, and the method of producing the improved slider head.
2. Description of the Related Art
Magnetic head slider assemblies for sensing or xe2x80x9creadingxe2x80x9d magnetically stored data on rotating disc drives are used extensively in computers and other devices where magnetic data storage means are employed. A head assembly includes a suspension and an xe2x80x9cair-bearingxe2x80x9d slider for carrying a magnetic transducer or sensor proximate the rotating disc. An actuator arm positions the air-bearing slider and sensor over individual data tracks on the continuously rotating disc surface. A gimbal provides a resilient connection which allows the slider to follow the topography of the rotating disc. The so called xe2x80x9cair-bearingxe2x80x9d refers to the phenomena, described in more detail in the specification, that creates a positive pressure air pocket between the slider and disc that keeps the slider above the disc, thus the slider xe2x80x9cfliesxe2x80x9d relative to the disc.
More specifically, the slider may include at least a pair of side rails which are positioned along its side edges and are disposed about a recessed area. The side rails form a pair of air-bearing surfaces. As the disc rotates, the disc drags air under the slider and along the air bearing surfaces in a direction approximately parallel to the tangential movement of the disc. As the air passes beneath the side rails, friction on the air-bearing surfaces causes air pressure between the disc and the air-bearing surfaces to increase, thus creating a hydrodynamic lifting force that causes the slider to lift and thus xe2x80x9cflyxe2x80x9d above the disc surface.
Magnetic head sliders are conventionally formed on a substrate in a row or a series of rows, each row having a plurality of heads. Once the heads are fabricated, the substrate is cut to form a row of heads in a side-by-side orientation. While still in a row formation, the thin film magnetic heads are lapped to a predetermined throat height dimension which is very critical to head performance. Once the desired lapped throat height dimension is achieved, this height should ideally be unaffected by subsequent processing of the head in order to achieve optimal performance of the head.
There are several subsequent processes steps in manufacturing the sliders. As a common aspect of the processing of the magnetic head, ion milling is employed. In an ion milling process as it applies to making magnetic sliders, photoresist is spin coated onto the slider. The photoresist is patterned to expose what will become the negative pressure cavity or recessed region between the air-bearing rails of the slider. Finally, the photoresist is removed. This ion-milling process is used to etch a region from the surface of a substrate.
The subsequent steps in the processing of the head form the pattern of the air-bearing rails, thus forming the air-bearing surfaces. Over time, the desired pattern of rails has become increasingly more complex in design so that a dry processing technique such as an etching process is generally used.
There are other uses for protective coatings. When the slider is in use, the rails typically fly within ten microinches from the moving disc. The head can sometimes come into inadvertent contact with the magnetic disc. Thus, the thin film magnetic head is also given a protective coating to protect from this inadvertent contact during use.
Chang et al. (U.S. Pat. No. 5,271,802, assigned to the assignee of the present invention) disclose a method of coating the magnetic head slider in order to protect the head during subsequent processing and during use. Chang et al. disclose a method of coating the slider with a three-layer protective surface made of silicon/carbon/silicon, the first silicon coat being an adhesive layer, and the third silicon layer being a masking layer. The carbon layer is the primary protective layer. This layer on the sliders greatly enhances the lifespan of the slider by protecting the surface from the processing steps that the head undergoes, as well as from conditions faced during the use of the slider in a device such as a computer, conditions such as corrosion due to exposure of the head to natural conditions of humidity, chemical wear, and physical contact with the moving disc.
While the Chang et al. invention improves upon the performance and lifespan of magnetic head readers, over time wear and environmental factors slowly decrease the effectiveness of the carbon coating. It is thus of great interest to improve the protective nature of the carbon coating. One way in which the coating can be improved is to enhance the coverage interface between the substrate surface and the carbon layer. Providing a smoother and cleaner substrate surface would enhance the coverage, and thus a method of improving the surface of a substrate is desired.
To date, ion milling has not been employed to improve the nature of the surfaces to be coated by metal or carbon. Gee et al. (U.S. Pat. No. 4,624,736) disclose a general technique of an ion milling process in conjunction with light activation and its use in the modification of a substrate surface. The process entails generating radical ion species and subjecting the surface to be etched to the incident radical species. This technique employs chemically reactive gases such as silane and carbon tetrafluoride and incorporates the use of UV-emitting laser light. This technique is used to etch and/or deposit chemical species on the surface of a substrate in an area outlined by the beam of laser light.
What is not disclosed in the prior art is a means of improving the coverage of the protective carbon layer on the surface of the slider or other surface using ion milling or other means. Due to the improved life span of the slider when protective carbon layers are employed, it is of great interest to increase the effectiveness of this layer. Thus, what is needed is a means of improving the surface of a substrate prior to depositing a mask, which can be a chemical or metal species, or etching the surface. This invention is directed towards such an improvement.
It is therefore one object of the present invention to provide a method of smoothing the surface of a substrate, in particular a magnetic head slider/sensor (hereinafter slider), using an ion milling technique.
It is another object of the present invention to provide increase the coverage of the protective carbon coating on a magnetic head slider, thus improving the lifespan of the slider.
It is yet another object of the present invention to provide a method of protecting the slider surface from subsequent processing as well as the final air-bearing rails that are exposed to the environment and physical contact with the disc.
The foregoing objects are achieved as is now described. A method is provided of smoothing the perturbations on the surface of a magnetic head slider, the method comprising several steps. First, at least one air-bearing surface to be smoothed is provided. Next, an ion species is generated from a defined source to form a beam of incident radiation. The beam has a linear axis emanating from the source and thus forms an angle of incident radiation with respect to the surface to be smoothed. Finally, the at least one surface is smoothed by exposing the surface(s) to be smoothed to the beam of incident radiation, where the angle of incident radiation is less than 90xc2x0 relative to a vertical axis drawn perpendicular to the surface to be smoothed.
To make a corrosion resistant magnetic head slider, the method further comprises coating the smoothed surface with a layer of amorphous carbon. This protects the surface from corrosion and physical impacts. The angle of incident radiation of the method of the invention is between about 40xc2x0 and 90xc2x0 relative to the vertical axis of the surface(s) to be smoothed. The beam of radiation is typically between about 200 and 500 volts and a current density between about 0.3 and 1.0 mA/cm2. The carbon layer is typically between about 20 and 1000 Angstroms. There can also be an adhesive layer placed on the smoothed surface before the carbon layer is added. The various layers are deposited using magnetron sputtering or ion beam deposition.
The above as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.